/*
day449 
2020.11.19 
*/

#include<iostream>
#include<vector>
using namespace std;

class Solution {
public:
    int trailingZeroes(int n) {
		int res=0;
		for(int len=1;len<=n/5;)
		{
            len*=5;
			for(int i=0;i<=n-len;i+=len)
			{
				res++;
			}
		}
		return res;
    }
};

int main()
{
	Solution s;
	cout<<s.trailingZeroes(5);
	return 0;
}
